feat: Add NL2SQL query interception in MySQL_Session

- Add NL2SQL handler declaration
- Add routing for 'NL2SQL:' prefix
- Return resultset with generated SQL and metadata

include/MySQL_Session.h

@@ -284,6 +284,7 @@ class MySQL_Session: public Base_Session<MySQL_Session, MySQL_Data_Stream, MySQL
 	void handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_COM_INIT_DB_replace_CLICKHOUSE(PtrSize_t& pkt);
 	void handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_COM_QUERY___not_mysql(PtrSize_t& pkt);
 	void handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_COM_QUERY___genai(const char* query, size_t query_len, PtrSize_t* pkt);
+	void handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_COM_QUERY___nl2sql(const char* query, size_t query_len, PtrSize_t* pkt);
 #ifdef epoll_create1
 	/**
 	 * @brief Handle GenAI response from socketpair

lib/MySQL_Session.cpp

@@ -3789,6 +3789,109 @@ void MySQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
 #endif  // epoll_create1 - fallback blocking path
 }
 
+// Handler for NL2SQL: queries - Natural Language to SQL conversion
+// Query format:
+//   NL2SQL: Show me top 10 customers by revenue
+// Returns: Resultset with the generated SQL query
+void MySQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_COM_QUERY___nl2sql(const char* query, size_t query_len, PtrSize_t* pkt) {
+	// Skip leading space after "NL2SQL:"
+	while (query_len > 0 && (*query == ' ' || *query == '\t')) {
+		query++;
+		query_len--;
+	}
+
+	if (query_len == 0) {
+		// Empty query after NL2SQL:
+		client_myds->DSS = STATE_QUERY_SENT_NET;
+		client_myds->myprot.generate_pkt_ERR(true, NULL, NULL, 1, 1240, (char*)"HY000", "Empty NL2SQL: query", true);
+		l_free(pkt->size, pkt->ptr);
+		client_myds->DSS = STATE_SLEEP;
+		status = WAITING_CLIENT_DATA;
+		return;
+	}
+
+	// Check AI module is initialized
+	if (!GloAI) {
+		client_myds->DSS = STATE_QUERY_SENT_NET;
+		client_myds->myprot.generate_pkt_ERR(true, NULL, NULL, 1, 1241, (char*)"HY000", "AI features module is not initialized", true);
+		l_free(pkt->size, pkt->ptr);
+		client_myds->DSS = STATE_SLEEP;
+		status = WAITING_CLIENT_DATA;
+		return;
+	}
+
+	// Get NL2SQL converter from AI manager
+	NL2SQL_Converter* nl2sql = GloAI->get_nl2sql();
+	if (!nl2sql) {
+		client_myds->DSS = STATE_QUERY_SENT_NET;
+		client_myds->myprot.generate_pkt_ERR(true, NULL, NULL, 1, 1242, (char*)"HY000", "NL2SQL converter is not initialized", true);
+		l_free(pkt->size, pkt->ptr);
+		client_myds->DSS = STATE_SLEEP;
+		status = WAITING_CLIENT_DATA;
+		return;
+	}
+
+	// Build NL2SQL request
+	NL2SQLRequest req;
+	req.natural_language = std::string(query, query_len);
+	req.schema_name = client_myds->myconn->userinfo->schemaname ? client_myds->myconn->userinfo->schemaname : "";
+	req.allow_cache = true;
+	req.max_latency_ms = 0; // No specific latency requirement
+
+	// Call NL2SQL converter (synchronous for Phase 2)
+	NL2SQLResult result = nl2sql->convert(req);
+
+	if (result.sql_query.empty() || result.sql_query.find("NL2SQL conversion failed") == 0) {
+		// Conversion failed
+		std::string err_msg = "Failed to convert natural language to SQL: ";
+		err_msg += result.explanation;
+		client_myds->DSS = STATE_QUERY_SENT_NET;
+		client_myds->myprot.generate_pkt_ERR(true, NULL, NULL, 1, 1243, (char*)"HY000", (char*)err_msg.c_str(), true);
+		l_free(pkt->size, pkt->ptr);
+		client_myds->DSS = STATE_SLEEP;
+		status = WAITING_CLIENT_DATA;
+		return;
+	}
+
+	// Build resultset with the generated SQL
+	std::vector<std::string> columns = {"sql_query", "confidence", "explanation", "cached"};
+	std::unique_ptr<SQLite3_result> resultset(new SQLite3_result(columns.size()));
+
+	// Add column definitions
+	for (size_t i = 0; i < columns.size(); i++) {
+		resultset->add_column_definition(SQLITE_TEXT, (char*)columns[i].c_str());
+	}
+
+	// Add single row with the result
+	char** row_data = (char**)malloc(columns.size() * sizeof(char*));
+	row_data[0] = strdup(result.sql_query.c_str());
+
+	char conf_buf[32];
+	snprintf(conf_buf, sizeof(conf_buf), "%.2f", result.confidence);
+	row_data[1] = strdup(conf_buf);
+	row_data[2] = strdup(result.explanation.c_str());
+	row_data[3] = strdup(result.cached ? "true" : "false");
+
+	resultset->add_row(row_data);
+
+	// Free row data
+	for (size_t i = 0; i < columns.size(); i++) {
+		free(row_data[i]);
+	}
+	free(row_data);
+
+	// Send resultset to client
+	SQLite3_to_MySQL(resultset.get(), NULL, 0, &client_myds->myprot, false,
+	                 (client_myds->myconn->options.client_flag & CLIENT_DEPRECATE_EOF));
+
+	l_free(pkt->size, pkt->ptr);
+	client_myds->DSS = STATE_SLEEP;
+	status = WAITING_CLIENT_DATA;
+
+	proxy_debug(PROXY_DEBUG_NL2SQL, 2, "NL2SQL: Converted '%s' to SQL (confidence: %.2f)\n",
+	            req.natural_language.c_str(), result.confidence);
+}
+
 #ifdef epoll_create1
 /**
  * @brief Send GenAI request asynchronously via socketpair
@@ -6759,6 +6862,13 @@ bool MySQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
 			handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_COM_QUERY___genai(query_ptr + 6, query_len - 6, pkt);
 			return true;
 		}
+
+		// Check for NL2SQL: queries - Natural Language to SQL conversion
+		if (query_len >= 8 && strncasecmp(query_ptr, "NL2SQL:", 7) == 0) {
+			// This is a NL2SQL: query - handle with NL2SQL converter
+			handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_COM_QUERY___nl2sql(query_ptr + 7, query_len - 7, pkt);
+			return true;
+		}
 	}
 
 	if (qpo->new_query) {